Equine Eyesight Basics

Equine eyesight is extremely important to horses, and has been throughout their evolution as prey animals. Their vision allows them to see potential danger at great distances. A horse’s total range of vision is thought to be as much as 350 degrees (Ball, 1999). That is almost a complete circle around the body!

However, horses also have blind spots that anyone working with them must be aware of. Understanding equine eyesight is very important for safety, training, and even assessing their athletic capability in different situations.

How Equine Eyesight Works

The horse has both monocular and binocular vision.

equine range of vision diagram — *Copyright Equine Network, LLC*

Monocular vision means the horse can see out of the right eye and the left eye independently. In other words, a horse’s right eye could be looking at a dog approaching from the right at the same time its left eye is looking at you approaching with a halter to catch it in the pasture.

Binocular vision refers to both eyes working in unison, looking at the same thing at the same time. A horse uses binocular vision to look at something “head on.” The horse will turn its head or even its whole body in an effort to use binocular vision and look at something with both eyes.

Research indicates a horse raises and lowers its head to better focus on a given object.

More About Vision

Monocular vision gives the horse a very large view of the world around it, enabling it to perceive potential danger all the way to the horizon along both sides of the body. This wide field of monocular vision makes the animal extremely perceptive of motion. Horses see even small movement at great distances—although not in much detail.

It is interesting to note that the pupil (the slit in the eye that allows light in) is more horizontal in the horse than in many other animals. (A cat’s pupil is more vertical, for example; a human’s is rounder.) The horizontal pupil allows for greater vision over a wide horizon.

Monocular vision is essential for the horse’s survival. It increases the animal’s ability to see and sense danger from which it can run away—what is called the “fright or flight” reaction. Horses typically prefer to run away from danger, rather than stay and fight, although they could do either.

A horse’s binocular vision is more acute than its monocular vision. Binocular vision allows the animal to see with greater detail by focusing on something with both eyes.

The range of a horse’s binocular vision is about 65 degrees directly in front of its head. This area of binocular vision is the only area where it sees objects in three dimensions—length, height, and width. Binocular vision allows the horse to see with better depth perception than does monocular vision.

However, it cannot use binocular vision for anything closer than 4 to 6 feet directly in front of it, as this area is one of the four major blind spots in the horse’s field of vision.

equine vision blind spot diagram — Copyright Equine Network, LLC

The four blind spots in an equine’s vision are:

Front of the Head—the area directly in front of the horse’s head when the animal is using binocular vision. As mentioned, experts estimate this blind spot typically ranges out 4 to 6 feet in front of the animal. It is triangular in shape.
Under the Head and Neck—The area directly under a horse’s head and neck is a blind spot as well. For this reason, a person should not cross in front of the horse in this area. Don’t duck under the head or neck of a horse that is tied or in crossties. Another thing to understand is that a horse’s speed of approach to an object can affect its ability to see the object. Repetition and mental conditioning can help train horses to negotiate successfully in situations, such as jumping and barrel racing, in which objects become more difficult to see as the horse nears them. The horse might lower its head in an effort to focus both eyes on the object and see it in more detail.
Over the Head, Neck, and Back—This blind area starts at the back of the eyes and continues over the top of the head, down the neck, and over the back to the dock of the tail. Have you wondered why a horse gets startled if you remove your jacket or shirt while mounted? Or why a horse is afraid of the clippers? The problem might not be the noise, but the fact that the animal can’t see what’s causing the noise!
Behind the Horse—The area directly behind, to the width of the animal’s rump, is another complete blind spot. Even when the horse turns its head to see behind itself, at best it is only using one eye—monocular vision, which can see long distances but with little detail or depth perception.

Anyone who works with horses must remain aware, at all times, that a horse cannot see its handler, or anything else, in its blind spots. This is a safety issue, because something the horse cannot see, or cannot see clearly, can startle or frighten it. Any time you’re around horses, you must stay aware of what they might be thinking.

More About Equine Vision

More interesting information about the equine eyesight:

The size of the horse’s eyeball (known as the globe) is larger than that of any other mammal, including the elephant and the whale.
Horses see better at night than humans do.
Humans are believed to have better overall eyesight than horses, even though horses can see motion at much greater distances than humans do.
Experts believe eyesight capability varies among horses, just as it does among humans. (In other words, some horses can see better than others.)
Recent research indicates horses can see some colors, although they can’t see red.

This article was adapted from “Equine Science: Basic Knowledge for Horse People of All Ages,” By Jean T. Griffiths. Copyright Equine Network.